Field
Embodiments of the invention relate to memory access. More specifically, embodiments of the invention relate to memory access in a T type memory topology for dual inline memory modules.
Background
There are two popular types of memory topologies commonly used with dual inline memory modules (DIMM): daisy chain topologies, and T type topologies. Daisy chain topologies generally provide inferior performance to T type topologies where two DIMMs exist per channel especially when performing a read from or write to the closest DIMM. This is due to the signal distortion as a result from the reflection between the two DIMMs. With T type topologies, it is important to have balanced loads on each branch of the T. However, some systems exhibit a T topology that leaves one DIMM slot unloaded. This results in a stub and as a result, reflections on the stub. Such reflection seriously degrades signal integrity and, as a result, the memory interface may need to operate at a lower speed, which will reduce the memory bandwidth. It may be possible to mitigate this effect by installing a dummy load card in the unpopulated DIMM slot. To be effective, this would require dummies matching loads of the various possible DIMMs installed in the other slot.